Proximity sensing devices operate under a variety of principles, including inductive proximity sensors, capacitive proximity sensors and optical proximity sensors. Optical proximity sensors or switches are generally comprised of a light-emitting or transmitting component, typically a diode, and a receiving component, typically a photodiode. Among the different types of proximity sensors or switches is a reflection system, in which the transmitter and receiver are typically integrated into a single unit or device. In one type of reflection system, the light emitted by the transmitter in the transmitter/receiver device is transmitted into the area to be monitored. As long as there is no object in the area to be monitored, no light is reflected back to the receiver in the transmitter/receiver. However, if an object enters into the area to be monitored at least part of the transmitted light is reflected by the object and can be detected by the receiver in the transmitter/receiver.
For such optical sensor systems, it is necessary to exactly align the transmitting and receiving components of the optical sensor devices during manufacture and installation so that the light emitted by the transmitter is incident via reflection on the receiver for the desired monitoring range. Accordingly, manufacturing such optical sensor systems can be costly. Moreover, each transmitting/receiving unit only operates in one direction, so if a particular application calls for being able to monitor in two directions, such as monitoring on both a horizontal and vertical axis or direction sensing (clockwise vs. counterclockwise) for a motor, etc., two separate transmitting/receiving units are required, adding to the expense. Additionally, such optical sensor systems require a controller, typically an IC, to implement the driver for the light transmission, signal filtering, etc. These IC controllers are manufactured separately from the transmitting/receiving unit of the optical sensor device and typically connected to the transmitting/receiving unit at installation of the optical sensor system, which, depending on the number of transmitting/receiving units operating, can require significant design effort to implement.